Anorexia Nervosa - Food for the Brain

Anorexia Nervosa

Every eating disorder varies person to person, and Anorexia Nervosa is no different. Anorexia is defined medically as a “loss of appetite.” This may be due to unconscious biological reasons (such as caused by anxiety, athletes’ triad or illness which can reduce appetite) or psychological reasons (because a person consciously restricts what they eat and drink) or both (Feast, 2022).  

Though manifestations of the disorder differ for each patient, many may develop food behaviours and rules around food, to limit appetite and maintain or reduce a very low body weight. They may try to avoid foods with too high calories, fat or carbohydrates and only eat “safe” foods they feel will not cause weight gain. They may have compensatory behaviours to remove calories they eat, such as using exercise or laxatives, may take appetite suppressants or use behaviours to reduce appetite, and may experience cycles of bingeing or purging.  

For a patient of anorexia, large aspects of self-esteem and self-worth are placed on personal weight, with weight-gain seen as failure. They may have body dysmorphia, where they believe they are larger than they are and ignore the risks associated with a low weight. They usually develop a huge fear of gaining any weight. They may refuse to accept diagnosis, be resistant to treatment and challenge all those that encourage weight gain.  

Signs of Anorexia:  


There are many potential causes of anorexia: 

  1. Genetics: there is a large body of evidence from researchers across the world, that has shown a large genetic influence on the acquisition of an eating disorder. 
  2. Stress and anxiety: Stress, (acute in response to a stressor) and anxiety (chronic in response to perceived stressor), trigger the “flight and fight” biological survival mechanism. As part of this, the brain and body focus on giving energy and Adrenaline to the muscles to run from a perceived stressor (as our human caveman ancestors ran from sabre toothed tigers) and threat. This reduces gastric motility, reducing blood flow to the gut and slows digestion which reduces appetite. With reduced appetite, weight loss is often inevitable. Trauma is also a cause as this can cause post-traumatic stress disorder (PTSD) and associated anxiety. Personality traits such as perfectionism, high ambition and self-pressure, and an environment where an individual does not feel in control of their own lives, will also increase stress and anxiety, and put a person more at risk of anorexia.  
  3. Society: an environment that places much self-esteem and self-worth emphasis around weight and health is often associated with eating disorders.         
  4. Athletes Triad: This is a condition in which an energy deficiency (with or without disordered eating or mismanaged nutrition), testosterone and oestrogen reduction, amenorrhea (absent menstruation) and bone loss (osteoporosis) occurs in athletes such as male and female long-distance runners with incredibly low body fat percentage.  

Long term effects 

The short-term effects of anorexia may provide a sufferer with short-term relief. However, the long-term effects vary from Osteoporosis (as amenorrhea, a lack of oestrogen which supports bone formation in females and insufficient dietary calcium in both males and females damage bones) to weakened immune system, heart and liver problems and infertility.  


  1. Re-nutrition: dependent on the severity of the case (not all anorexics are severely underweight, some just maintain a very low weight chronically), a sufferer must return to a healthy weight. To prevent re-feeding syndrome in severe cases and reduce the risk of relapse, this must be done in controlled and supported way, with a meal plan and gradual steps up. This is best orchestrated under professional care under an eating disorder care hospital (inpatient, outpatient, or day units). It can also involve a tailored meal plan, with specific mineral and vitamin foods prescribed or supplemented, to restore nutritional deficiencies. Calcium containing foods and supplements are often given to stop osteoporosis. Some women are also put on the pill or HRT to increases Oestrogen and prevent bone decay, but this is controversial as it can mask the symptoms of the eating disorder and pre-long recovery.  
  2. Psychological support: To treat the causes of anxiety and reduce the fear associated with weight gain. This can be in the form of medication, therapy (from family to psychodynamic to CBT to mindfulness; what works best varies for each patient) and relapse prevention support. Often getting an eating disorder is not a choice, but recovery can be. Some recover fully, some patients stay stuck in quasi-recovery at a chronic sustained body-damaging low weight, and some never leave a critical undernourished state. With the right support and sustained care, full recovery is possible. 

Nutritional support 

There are stages of anorexia nutritional recovery, linked to the severity of the disorder.  

Stage 1: Refeeding. If severely underweight, it is important that a person does not gain weight too fast, as this can cause re-feeding syndrome. This is when metabolic disturbances in magnesium, phosphate, iodine, and potassium occur because of rapid nutrition following a fast, famine or malnutrition event. It can cause electrolyte unbalances resulting cardiac, pulmonary, and neurological symptoms and be lethal. Therefore, there must be gradual step ups in food and liquids over a sustained period. The first stage of re-nutrition is about targeting the nutritional deficiencies, often following a blood analysis by a GP or hospital where these are diagnosed. Most often these deficiencies lie in potassium, magnesium, thiamine, and calcium levels. A specific diet plan (with medicinal supplementation if required) will be given to target these deficiencies.  

Stage 2: Weight gain. A patient will then be put on a specific meal plan which will increase their calories by x amount each week (depending on the patient), creating a nutritional surplus which will return their bodies to a healthy weight. This is usually 500 calories extra a week to gain 0.5kg (in the same way that severely Obese patients have nutritional deficit meal plans with 500 calories less to lose 0.5kg a week). They will initially have exercise restricted and then encouraged as part of a sustainable, balanced lifestyle and improved mental health. This diet plan will involve three large meals and snacks and be monitored by professionals, with regular weigh-ins and blood tests, to monitor health. For best results, this will be accompanied by psychological therapy, to treat the causes of the eating disorder, prevent relapse and help develop a more balanced thinking around weight, self-esteem, and body image. Emphasis will be placed on removing the link between food and feelings.  

Stage 3: As a patient’s weight increases, the nutritional plan can shift to improve the psychological, stress response to weight and food, and improve an individual’s relationship with “fear foods” (often those high in calories, carbohydrates and fat and considered weight gain foods). This can be with “desensitisation,” where an individual is gradually exposed to all their fear foods in a controlled and planned way (to prevent binge-restrict cycles or calorie compensation), to encourage them to see the pleasure from the tastes, the nutritional benefits to their health long-term and memories associated with the food. This stage is about removing the emphasis from food solely around weight loss or gain and reminding the individual of the benefits of food in happiness and health.  

Stage 4: Set point. When an individual reaches a target set point weight in the healthy BMI range, they are put on a maintenance diet by eating disorder facilities. Gradually, the patient will learn how to eat more intuitively, based on hunger and fullness satiety signals, eating a balanced diet for energy and pleasure.

Researched by: Laurentia (Laura) Campbell. Neuroscience and Nutrition scientist (with focus on the gut microbiota and omega 3) and writer. Former anorexic and binge eater turned gourmet food connoisseur, researcher, writer, marketer, and evidence-based nutritionist. See and